The present invention relates to novel pile carpet containing therein carbon fibers, having excellent antistatic property even under the humidity lower than 40% R.H., and the method for production thereof.
There have been widely used pile carpets produced by tufting synthetic fiber or natural fiber such as wool onto the primary backing.
When a man walks on such carpets, static electricity is generated by rubbing the shoe soles and the carpet. The static charge often imparts to the human body a shock by discharge, for instance, touching a metal door knob. In general such electrical shock becomes troublesome when the charge exceeds 3000 volts. On the other hand, the maximum charge of the carpets used in a room for electronic equipments such as computers, which are very sensitive to static electricity, much be kept below 1500 V.
Heretobefore, many procedures have been proposed for the prevention of the built-up of static charge.
The first is a method using conductive fibers such as metallic or metalized fibers with conventional natural or synthetic fibers as pile yarns. This method, however, impairs the surface appearance of the produced carpet because of metallic or black color of the conductive fibers themselves.
Moreover, since physical and chemical properties such as Young's modulus, elongation and dyeability of the conductive fibers are generally different from those of conventional fibers to be mixed therewith, when the pile produced therefrom is subjected to dyeing and finishing or heat treatment, the difference in shrinkage appears between the mixed fibers to impair quality of the produced carpet. Furthermore, higher antistatic effect (less than 1500 V) at a low humidity (lower than 20% R.H.) can not be attained at all by this conventional method. The second is a method using antistatic fibers.
However, the carpet produced by this method has a disadvantage lowering the antistatic effect under atmospheric humidity below 40% R.H. The third is a method adding antistatic agents or conductive powder such as metallic or carbon powder into the back coating latex.
This method, however, also has disadvantages that the antistatic effect is lowered under atmospheric humidity lower than 30% R.H., and the added agents gradually bleeds out while being used, and it is necessary to add a relatively large amount of the antistatic agent (5-35% by weight) in order to attain sufficient antistatic effect. Another conventional method is to add conductive fibers such as carbon fiber into latex (U.S. Pat. No. 3,746,573). This method had an advantage that good antistatic effect is obtained without any change in the surface appearance of the produced carpet and in the pile quality. This method has the following disadvantage.
The antistatic effect is not sufficient under an atmospheric humidity lower than 40% R.H. and a relatively large amount of carbon fibers have to be added into the latex in order to attain sufficient antistatic effect, and therefore mechanical properties of latex in the backing layer tend to deteriorate. Adding a large amount of carbon fibers, it is difficult to disperse them uniformly and the added carbon fibers aggregate to be lumps circumferentially in the back side of the produced carpet. Therefore, the adhesive power of the latex is further lowered to cause deterioration in the durability of the carpet. Moreover, in the backing process, the added carbon fibers tend to adhere to the roller to interrupt the backing process. Thus the amount of carbon fibers added into latex in this conventional method is substantially limited.
An object of the present invention is to provide novel carpets having excellent antistatic property even under the condition of humidity lower than 40% R.H.
A another object of the present invention is to provide carpets having excellent antistatic property without lowering other characteristics such as an appearance, chemical and physical properties.
A further object of the present invention is to provide carpets having excellent antistatic property, being backed with latex, containing therein a relatively small amount of carbon fibers which does not lower the adhesive property.
Those above will become more readily apparent from the following detailed description and examples.